Asbestosis

It is the only pneumoconiosis itself that is produced by exposure to asbestos, being defined as a disease caused by the accumulation of dust in the lung tissue (in this case, asbestos), causing a non-neoplastic reaction in it.

Asbestos is the generic name of a group of silicates with a double characteristic: resistance to high temperatures and their arrangement in fibers. Among them, we highlight: chrysolite, crocidolite and amosite. They have exceptional properties for thermal and electrical insulation.

The asbestosis is characterized by lung fibrosis extending to the visceral pleura and parietal respects.

This disease can be considered the second most important pneumoconiosis, after silicosis, and is associated with pleural lesions.

Causes of asbestosis

Asbestosis occurs from exposure to asbestos. The sources of exposure are:

• Pipe mounting.
• Boilermakers and other construction workers.
• Mining.
• Rolling and manufacturing of asbestos products.
• Manufacture of fire protection blankets and fire retardant clothing.
• Plastic materials.
• Tile cement.
• Friction materials (brakes, clutches).

Since 1975 its use has been partly replaced by manufactured mineral fibers (fiberglass, waste wool).

If the exposure is very intense, it can appear after a few years, but, in general, it develops between 10 and 15 years.

Significant and sustained exposure is required for asbestosis to occur. The best way to measure exposure is the quantification of fibers retained in the lung or “fiber load”, which, related to the disease, is found to:

a) Asbestos fibers exist in healthy lungs of the general population;
b) asbestosis and fibrosis in the airways are related to high contents of chrysolite and amosite, and
c) mesothelioma is related to high amount of chrysolite, with the so-called “black spots”.

How does it originate?

Asbestos fibers reach the lung parenchyma and induce a reaction where they touch it, producing an accumulation of macrophages and neutrophils in the alveoli. This creates inflammation and then fibrosis around the asbestos fiber. There is as a consequence of the asbestos deposit:

• Thickening of the alveolar wall.
• Cell desquamation in the alveolar lumen itself.
• Peribronchial fibrosis in early stages.

Asbestos bodies present in sputum, bronchial aspirate (BAS), bronchoalveolar lavage (BAL) and / or lung or pleural tissue are not signs of disease, but rather of present or past exposure and, furthermore, they are not exclusive to asbestos inhalation , also observed after exposure to talc (talcosis) and other fibrous mineral elements.

Their existence and their number depend on the intensity and duration of the exposure, on the one hand, and on the absorption capacity of the lung parenchyma, on the other.

Symptoms of asbestosis

Symptoms are usually scarce and unspecific:

• The cough is dry, unless it coexists with the smoking habit.
• The most relevant clinical finding is dyspnea, first on exertion, which progressively increases until resting.
• Clubbing (present in up to 50% of cases) is a specific and typical sign of this type of pneumoconiosis, although it may exist in other diffuse pulmonary interstitial diseases.
• On pulmonary auscultation, bilateral end-inspiratory crackles appear, which are not modified by coughing or deep respiratory movements; it is the most characteristic clinical sign (in 95% of cases). Its posterobasal location, particularly subaxillary, is typical.
• To these signs and symptoms we could add: chest pain (30-50%) and expectoration (40-60%).

The evolution of the disease is slow but inexorable, and throughout it we can find various complications, among which we highlight:

• Chronic non-hypercapnic respiratory failure and Cor pulmonale , that is, a pO2 less than 60 mm Hg. It arises after many years of exposure and not on a regular basis.
• Bronchopulmonary neoplasia:
  – The joint effect between asbestos and tobacco determines the elevation of the prevalence of lung carcinoma in asbestos workers who are smokers.
  – These are usually adenocarcinomas, small cell carcinoma or squamous carcinoma.
  – They generally settle in basal or peripheral areas with abundant fibrosis, making their detection difficult in radiology and bronchofibroscopy.
  Unmistakable signs of bronchopulmonary neoplasia would be: the sudden appearance of clubbing in an individual exposed to asbestos or affected by asbestosis, or the existence of atypical malignant cells in the sputum or bronchial aspirate.
• Malignant peritoneal mesothelioma: less prevalent than pleural mesothelioma, it tends to be associated with pulmonary asbestosis, unlike pleural mesothelioma, which occurs more frequently in isolation.
• Caplan syndrome: it is rare, with clinical and radiological characteristics similar to silicosis, although without a tendency to tuberculosis infection.

How is it diagnosed?

The diagnosis is based on the clinical and physical examination that we have commented in the previous section, completing it with:

• Radiology: irregular linear images, preferably located in lower fields. As the disease progresses, it acquires a bilateral reticular interstitial pattern, which can even affect the middle lobes, but respecting the upper ones. There is a «sagging» of the cardiac silhouette (porcupine image), which is observed in advanced cases, and which appears to be due to fibrosis of the mediastinal pleura and surrounding lung tissue. A characteristic feature of asbestosis is the frequent association with lesions pleural, in the form of thickening of the parietal sheet, with or without calcifications, also related to asbestos exposure, and due to the presence of hyaline plaques.
• Thoracic CT: assessing in greater detail the degree of extension of associated fibrotic and / or calcified pleural lesions, and may complement the limitations of conventional chest radiography, but is of no special interest in assessing the degree of extension of parenchymal involvement pulmonary. (Sometimes, instead of a conventional CT, a CT scan is performed, observing characteristic alterations with curvilinear subpleural lines that appear parallel to the pleural surface.)
• Gallium lung scan, quantifying the degree of alveolitis, but with little specificity.
• Pulmonary function study (spirometry): there is a restrictive ventilatory pattern with a decrease in DLCO (this being the test that is altered earlier).
• Bronchofibroscopy: BAL shows a significant increase in neutrophils and the presence of ferrous bodies in the biopsy.

Asbestosis treatment

There is no treatment whatsoever, with the exception of the use of symptomatic measures.

The most effective, as always, is the application of preventive measures that prevent the development of pneumoconiotic lesions. Wearing masks during work, short stay in risky places, use of vacuum cleaners to clean clothes (both asbestosis and mesothelioma can be found in women with environmental exposure when cleaning the clothes of high-risk workers) …

When should I see a doctor?

Faced with dyspnea on exertion that increases progressively, without an apparent cause that justifies it (such as a significant weight gain, restarting exercise after prolonged rest due to another cause, etc.).

The history of the exposure (whether of a professional nature or others, such as asbestos-coated stoves, fire-retardant clothing, etc.) should be brought to the attention of the doctor immediately, which will help the diagnosis without delay of the pathology originating in your clinic. .